Keeping pigs healthy on pasture

by Sally Colby

Clean pastured pigs might be an oxymoron, but Dr. Elizabeth Hines, Penn State Extension swine specialist, said cleanliness is the first biosecurity step in raising pasture-based pigs.

“Biosecurity is about keeping animals healthy,” said Hines. “We don’t want disease to spread to get other animals sick; we don’t want sick animals to spread diseases to healthy animals. Always keep in mind the herd population and how you’re are keeping the herd healthy.”

For those who raise pigs in a commodity setting, biosecurity involves a checklist. Workers shower in, wear barn-dedicated clothing and boots throughout the work period, then shower out. Employee interactions with pigs outside the operation are usually prohibited.

But pastured pig operations vary widely, and establishing standards can be difficult. With such operations, Hines said it’s a matter of applying the principles of biosecurity to prevent the spread of disease rather than keeping animals totally isolated.

Hines explained the USDA definition of biosecurity: “The key phrase is ‘to keep diseases and pathogens that carry them away from livestock, property and people.’ We can use physical interventions to keep diseases and pathogens away from livestock, property and people.”

Biosecurity concepts are based on how diseases move. “It’s either keeping as many diseases out as possible, or creating a separation to prevent diseases from entering the farm of healthy animals,” she said.

The “line of separation” concept is key to effective biosecurity. It separates “clean” from “dirty” and is integral in establishing movement restrictions for farm personnel, visitors, animals, manure-handling equipment and vehicles. The farm owner determines where disease transmission is likely to occur and analyzes that risk to set boundaries.

In establishing lines of separation, the farm owner designates three zones on the farm. A restricted access zone is a high-risk area in and around livestock (housing or pasture). The transition zone is a medium risk area that includes the line of separation. A controlled access zone is an area with low to medium risk. The line of separation will help guide visitors and vehicles that enter the farm.

Pasture-based hog producers should develop an awareness of how pathogens move. Hines explained that pathogens can be moved by animals, items and people. “Pathogens can attach to an animal and make that animal sick,” she said. “Some pathogens will not make the animal sick but will still be carried around. Birds are famous for picking up pathogens and carrying them from place to place without getting sick.” Another source of contamination is through new animals introduced to the farm, so it’s important to purchase animals from reputable sources with health records available.

Wild animals can be serious threats to biosecurity on pastured pig farms. Groundhogs are commonly found in pastures, and can transmit brucellosis and leptospirosis to pigs. Other rodents and birds should be managed to eliminate the risk of introducing parasites and disease.

Poor mortality management can lead to biosecurity breaches, especially if deceased animals were sick, or if there’s a predator issue such as vultures or coyotes that get into an improperly maintained compost area. Anything that invites wildlife onto the property, such as improperly stored feed, can introduce a potential pathogen source.

Equipment that moves throughout the farm such as tractors, feeders, wheelbarrows and manure-handling equipment can move pathogens. Boots can pick up pathogens and should be limited to on-farm use and disinfected frequently.

A combination of pathogen load, exposure and time influence biosecurity. Pathogen load refers to the level of pathogens present in a particular space, on an infected animal or in a known contaminated area. Exposure refers to the number of opportunities to make contact with a pathogen – if the pathogen is only on a feeder and you don’t touch the feeder, chances of picking up that pathogen are fairly low. Time is how much time is spent near a potential exposure or in an area with a high pathogen load.

Of the influences that spread disease, some are easier to control than others. “It’s difficult to control the pathogen load … because we don’t know which pathogens are in that space or how many are there,” said Hines. “If we don’t know when a pathogen entered, and we don’t know how much was there or how long it’s been there, it’s difficult to estimate pathogen load in a given space.”

The amount of time spent in a potentially contaminated area can become a biosecurity risk. If a task requires working in a pen that contains sick pigs, those sick animals have been moving around the entire pen and potentially spreading pathogens throughout the area. In this case, washing clothing and disinfecting boots will be key in reducing the pathogen load.

To reduce pathogen levels in buildings, the goals are minimizing organic matter and enhancing air circulation. If a building is empty and being prepared for animals, remove bedding, expose porous surfaces and wash anything that can be washed. Promote air circulation by opening doors and using fans, and expose surfaces to sunshine and fresh air whenever possible.

“Daily dirt is easy to overlook,” said Hines. “Prioritizing it in your daily routine is a good practice to minimize pathogen spread. Personal hygiene is one way to keep pathogens from spreading around the farm.” She suggested developing the habit of cleaning footwear properly each day. A cleaning mat to disinfect dedicated boots, along with coveralls that will be removed prior to leaving the farm, helps limit the spread of disease. Workers should always wash hands between tasks, such as going from farrowing barn to nursery pigs, or after working outdoors prior to feeding.

If new pigs are coming to the farm, remember that it’s worth the time to observe a 30-day quarantine. New pigs should be handled/fed either last or by someone wearing clean boots and clothing. That person should not handle or feed other pigs until they’ve changed clothing, disinfected boots and washed hands.

An important biosecurity step is a developing a good relationship with a veterinarian. It’s important that the vet is familiar with healthy animals on the farm – if they only see sick animals, it will be more difficult to determine what’s normal and formulate a treatment plan. The vet can recommend appropriate disinfectants and help develop parasite management and vaccination protocols for breeding stock and animals on feed.

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